Data commit

Task/Range-expansion/Haskell/range-expansion-1.hs

@@ -0,0 +1,2 @@
+> expandRange "-6,-3--1,3-5,7-11,14,15,17-20"
+[-6,-3,-2,-1,3,4,5,7,8,9,10,11,14,15,17,18,19,20]

Task/Range-expansion/Haskell/range-expansion-2.hs

@@ -0,0 +1,10 @@
+expandRange :: String -> [Int]
+expandRange = concatMap f . split ','
+  where f str@(c : cs) | '-' `elem` cs = [read (c : a) .. read b]
+                       | otherwise     = [read str]
+            where (a, _ : b) = break (== '-') cs
+
+split :: Eq a => a -> [a] -> [[a]]
+split delim [] = []
+split delim l = a : split delim (dropWhile (== delim) b)
+  where (a, b) = break (== delim) l

Task/Range-expansion/Haskell/range-expansion-3.hs

@@ -0,0 +1,27 @@
+{-# LANGUAGE FlexibleContexts #-}
+
+import Text.Parsec
+
+expandRange :: String -> Maybe [Int]
+expandRange =
+  either
+    (const Nothing)
+    Just
+    . parse rangeParser ""
+
+rangeParser ::
+  (Enum a, Read a, Stream s m Char) =>
+  ParsecT s u m [a]
+rangeParser = concat <$> (item `sepBy` char ',')
+  where
+    item = do
+      n1 <- num
+      n2 <- option n1 (char '-' *> num)
+      return [n1 .. n2]
+    num =
+      read `dot` (<>) <$> option "" (string "-")
+        <*> many1 digit
+    dot = (.) . (.)
+
+main :: IO ()
+main = print $ expandRange "-6,-3--1,3-5,7-11,14,15,17-20"